Etv Bergvesenet Postboks3021,7002 Trondheim Rapportarkivet

Bergvesenetrapportnr InternJournalnr Interntarkiv nr Rapponlokalisering Gradering BV 606 Trondhebn APen

Kommerfra ..arkiv Eksternrapportnr Oversendtfra Fortroligpga Fortroligfradato: USB Sul 232-72-15

Tittel Progressreportof 1972 fieldworkon Numhovdprosjekt.Reconnaissancegeologynear depositson Skjønne(Rødberg)mapsheet.

Forfatter Dato • BedrIft Maleolin P Annis 1972 Sulfidmalin A/S

Kommune Fylke Bergdistrikt 1: 50 000 kanblad 1: 250 000 kartblad

Nore og Østlandske 16151

Fagornråde Dokumenttype Forekomster Geologi Duse Kisgang Hytte Loftsgård Lauvåsen

Råstofftype Emneord Malm/metall Cu Ag

Sammendrag ,41 r-/ 9 2

N C Corp c/ ; •

mno nd. 231 --31- Abstract Stratigraphicunitsstrikeapproximatelynorth-southand dip steeply both to the east and to tho west overmost of the map area. Fivemajor mnp unitsmakeup the stratigraphicsection. Theseare, fromwest to erwt,amphibolite,quartzite,porphyry,greenstonoand associatedrocks, and micaceousquartzite.At the 1:50,000map acale,copper-sulfideideposits occurin two narrowbeltswithinand near the greonstoneunit. One follows thewesternborderof the greenstones,withdepos'itslocatedwithina few metersto severaltensof metersof the contactwithquartziteand porphyry. The secondbelt is near the easternborderof the greenstoneunit within a few motersof the contactwith micaceousquartzite.One depositlies just beyondthe contactin Micaceousquartzite. At the deposits,magnetitebearingcountryrocksare cut by quartzveins. The quartzveinscontainchalcopyrite,malachite,borniteand, at three localities,tracesof molybdonito.Wall rocksare locallyimpregnated vithchalcopyriteovershortdistancesaway fromveins,and may be altered to a pinkcolor. The depositsare epigenetic.Theiroccurencein magnetite-bearing greenntonesin closeproximityto siliceousrock unitsis considered significant.'

Introduction Background Severalcopper-sulfidedepositsare knownto occurin Numedaland at Hovin. Theyare typicallysmall,so thatonlya few havebeen worked extensively.All miningoperationsin the area terminatedlongago. The map of minesand mineraldepositsof southNorway(Foslie1925) showsthe Numedaldepositstendto occuralonga north-southtrendingzone, The Hovinarea lieson the southernextensionof thislinearzone. No geologicbasisfor thislineartrendhas been previouslyestablished, becausea welldocumentedaccountof the regional'geologyis lacking.• Howeveran unpublishedbedrockmap,withouttext,indicateslithologic boundariesalso trendnorth-southin the Numedalarea ( ). Objectivesof thisstudy It is the aim of thisstudyto learnthe geologicframeworkin which thesedopositsoccurand,in particular,to identifylikelygeologiccontrols 2 whichproducedthe linoarbelt of mineralization.Furthormoreit is of interestto lOoMor an explanationfor localizationwithinthe belts, and to eee what can be learnedabout the natureof ore transportto the site of depoaition.

Acknowledgements ProfessorF. Vokessuggestedthisstudyand introducedme to the prnblemsinvolved. S. Bergstølassistedin this initialorientationand pointedout the abandonedlocalitiesto me in the field. It is a pleasure to acknowledgethoirsupportand discussions,and to Sointhis study of the -Hovinmineralization.A researchfundAdministeredby ProfessorVokesfor studiesof ore genesisprovidedfinancial support for thiswork to date.

Fieldprocedures Fieldwork consistedof traversesacrossstratigraphicunitsat widelyspacedintervals.Segmentsof selectedcontactswere walkedout, 1111 whileotherswere locatedfromair photographs.The depositswere briefly described,howevertheirpoor conditionand weathereddumpsdiscouraged extensivefieldstudyat thisreconnaissancestage. Fieldobservationswere locatedon 1:35,000air photographsin the fieldand subsequentlytransferredto the Skjønne1:50,000map sheet. Workin the fieldextendedfrom July 19 throughAugust2, 1972,and includedvisitsto depositson the Noremap sheetand at Hovinwith S. Bergstøl.

The StratigraphicUnits

Table1 comparesthe stratigraphicsequencediscussedhere with the Bandakseriesof the Telemarkformationgivenby Dons (1960). The general similaritybetweenthesesuggeststhe Bandakseriesextendsas far northas the Skjønnearea. Muchof the discrepancyon Tablet may be onlyapparent, for porphyrylenseeseemto occurat severalplacesin the section,including minorlensesin the greenstoneunit. The followingunitdescriptionsare takenentitelyfrom fielddescriptions.

Amphibolitehas beenmappedas a separateunit only in the southwest cornerof the map area. It is mediumgrainedand containsaboutequal amounteof plagioclaseand dark greenhornblende.

Quartziteunderliesa largeportionof the map area westof the greenstone 3

Table1

Comparieonof StratigraphicUnits

Skjønne(thisstudy) Bandakgroup(Dons1960)

--micaceousquartzite --quartzechiatwith conglomerate --marble(locallydevelored) --greenlava includingone layerof eanstonecontainingfoseils(?) --porphyry(acidlava)(maybe missidg locally) --greenstoneand associated --greenlavawith conglomerate,3-4 rocks,includingpebbly beds of quartzitewith conglomerate, quartrma meta-sandstone, irregularlyand locallydevelopedlayers ;itihOX"pbrphyrylenses,etc, of quertzschists.Cu-Agmineralization Cu-sulfidomineralization. -possibleunconformity --porphyrylenses --quartzite --quartzite(withconglomerate)of varyingthickness --porphyryof varyingthickness,locally miesing --basalconglomerateand quartzite,the thicknessdecreasingeastwardto zero --amphibolite

unit. It is a thickunit of nearlypurequartzitewith preservedcrosabedding and ripplemarksplusothersedimentarystructureshereand there. 'In additionto quartz,it containsa few biotitecrystalsand rare pyrite. 11, Basicdike-likeamphibolitebodies,10-15metersthick,occurin the quartzite.They have sharpcontactswithquartzite,neitherunit showingtexturalor mineralogicalmodificationeat the contacts;and they parallelthe quartzitebedding.

Porphyry lensesalso occurwest of the greenatoneunit. One is withinthe quartziteunit,whilethe otherone mappedoccursbetweenquartziteand greenetone.Typicalporphyryconsistsof a gray,aphaniticgroundmasswith smallwhitefeldeparlaths,andoftena greenmaficmineral,less than2mm as preservedphenocryets.It containslittleor no magnetite,is hard and glessy. Charactoriatic"flowbanding"can be seenin places. It can be concludedthat porphyry-formingextrusionsrecurredduringdepesition of the sedimentarysection. Oronnetoneandaneociatedrookeforma majorunitin thoOontralportion of thomaparea. Mostof the unit is greento gray,hardhornfels and nofterschietwith chloriteand greenamphiboleas characteristicminerals. Smalleagnetitecrystalsoccurin severalplaces,and is a commonaccessory. Srarietyof otherrock typeslocallyoccurwithinthe unitand seem to have been lensesand thinbeds in a formersedimentarysection. Theseinclude weaklymetamorphosedquartzosesandstone,oftenwith pebbles,locally strotchedand schiXtose,minorporphyry,exceedinglyfine-grained meta-shale,and a traceof meta-limestone(?).

Ilicaceousouartziteunderliesthe easternportionof the mappedareLi. It is lightcolored,and has More than80% quartz. Muscoviteis the mostchmracteristicmicaat mostexposures.Howeverbiotiteis present near the westernboundaryand againin the east. This is indicatedby thininternalcontactlineson the map. The micasparallelthe foliation and, whereabundant,imparta schiStosity.

Structuralfeatures.

The possibleUnconformitvlistedby Dons (seeTable1) is neither confirmednor rejectedby the work to date. More detailedexamination at and nearboth contactsof the greenstoneunit may clarifythisas wellas the proximityof ore.

Faultsare thoughtto be presentin more placesihanmarkedon the map. Linearphysiographicfeaturesin the greenstoneunit approximately parallelto atrikemay tracefaultsor shearzones. The Dusesdeposit (doscribedbelow)lieson one of these. In the southwestcornerof the map,amphiboliteis in faultcontact vith the quartziteunit.

Å trulylargefold appearsto be definedby the foliationin theserocks. The accompanyingplotof polesto foliationare identifiedaccordingto threelithologicgroups. Polesof the threegroupsare interspersed and formn continuousprogression,or belt,mlonga greatcircleof the atereogram.This is interpretedto reflectone largefold. Sedimentary structuresin the quartziteindicatesthe youngerrocksare to the east. Thia meansmost of the stratigraphicsectionin the area has been overturned, and thatmajorfoldinghas deformedtheserocks.

Noteson IndividualProperties

Dusea,Kiegangand thedepositat Hytte (calledLoftsgårdskjerpby Foslie) / all lio nt the wentern edgo of the greenetone unit, and will bo dencribed firet.

Dusesoccursin greenschistcountryrock. The workingsfollowa planar shearzonemarkedby thoroughlyfracturedgreenschstwall rock,and the ore-bearingquartzvein. Theseapproximatelyparallelthe strikeof foliationaway from the zone. The wall rockcontainemany parallel quartz-calciteveins,tracesof.malachite,and tinymagnetitecrystals. Coppersulfides,malachiteand tracesof molybdeniteoccuriiyihemined quartzveins. Similarrelationscan be seenat a prospectabout 100 meterssonth along the shearzone.

The host rockat Kisganais fine-grained,magnetite-bearinggreenschist. The ore occursin crosscuttingquartzveins. The'veins.are up to 25cm thickand forman intersectingnetwork. The ore mineral,chalcopyrite, occursin the quartzveins,whichalsohas a few opencavitiesand malachite. The mine is now floodedand partlycaved.

The Hyttedepositliesat the toe of a largedump madeduringextensive water-tunnelconstructionnearby. The exposedopeningis a smalltrench about2 X 15 meters. Here irregularquartzveinsagaincut fine-grained, magnetite-bearinggreenschist.Theseveinsare generally10-25cmthick, but onlylocallycontaincalcite,chloriteand coppersulfideminerals.

Lauvaasenand two "skjerps"formthe easterngroupof deposits.

Lauvaasenliesnear the easternborderof the greenstoneunit. The host rock is a purplishgray,magnetite-bearingporphyrylense,whichlocally becomespink. The ore is associatedwitha soriesof quartzveins. Many veinsparellelfoliationand are barren,even thoughoffshoots trending 411 acrossfoliationcontainchalcopyriteand, whereweathered,malachite. The aulfidemineralsare more concentratedalongquartzveinsin the pink coloredrockand near inclusionsof porphyryin the veins. In additionto qunrtz,the veinscontaincalcite,chlorite,coppereulfidesand tracesof molyhdenite.Malachiteis also presenton manysurfaces. The minedzone is lessthan 5 meterswide. Immediatelynorthof the mine,only four quartzveinswere seenin outerop. Theremay be more southof the mine beneaththe soilcover.

Tho southernskierp,or prospect,has relationssimilarto Lauvaasen.The depositis in dark gray,very finograinedhornfels. Near the ore it becomespinkcolored. Here a seriesof irregularquartzveinsnpproximately tho rogionnlfoliation.The wall rock is also minorallzodand has manyopen spaces. The ore zone is lessthan2 metersthick,and individualveinsare less than25cm thick..Theycontainquartz,calcite, chlorite,biotite,coppersulfides,molybdeniteanda traceof tourmaline(?). Magnetiteispresentin the gray rocksenclosingthedeposit.

The northern"skjerp" is not a trueprospect. It occursimmediatelybelow a low dam and apparentlyformspart.ofthedam foundation.It may have beenexposedduringdam construction.Thedepositliesimmediatelyeast of the contactbåtweengreenstoneandmicaceousquartzite.Porphyritic trar micaceousquartzitewithk-feldsparcrystalsaboutlcm across,andAbiotite insteadof muscoviteformsthe countryrock. It is cut by many quartzveins whichcontainbornite,malachite,alittlepyriteand a traceof azurite, as well as inclusionsofthe metamorphicrocks.

References

Dons,J. A., 19601Telemarksupracrustalsandassociatedrocks.in Holtedahl,0.,Ed.,Geologyof ,NorgesGeol.Undersek.nr.208.

Foslie,S., 1925,Syd-Norgesgruberof malmfoiekomster.NorgesGeol. Undersek.nr.126. • POLES TO FOLIATION • (lower hernisphere)

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Quartzite, porphyry Greenschist and associated rock types Micaceous quartzite RECONNAISANCE GEOLOGIC MAP OF THE SW PORTION OF SKJØNNE MAP SHEET

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Greenstone and associated rocks ec Strike and dip ot innijtion (par all els bedlin) in quortiite MICCICCOUS quartr ite portly schistose locally over utned)

Porphyry Uni t cont,n_ t 5 lusned where approxirnutely loratedI Guartzite / where interred

Amphibohte Mineral deposi t

Luke:. 1”12 M Anrn.